Iron Speciation in Dissimilatory Fe(III)-reducing Cultures

A protocol has been developed for determination of iron distribution and speciation in the solid and liquid phases of dissimilatory Fe(III)-reducing bacteria cultures. Sampling methods and sample processing have been improved. Three different extraction conditions have been tested for iron measurement: hydrochloric acid, ammonium oxalate and hydroxylamine hydrochloride. Separate collection of samples for liquid and solids analysis was tested, providing the best insight into Fe distribution. One sample was taken from the aqueous phase after solid settlement in vials to determine the concentration of dissolved iron species; the other was taken from agitated flasks, in which iron was extracted from solids prior to the analysis. Extraction with HCl 1Mfor 24 h proved the least labor-intensive procedure, with extraction efficiency adequate for our purposes. The extractant properties of HCl, less aggressive than the others, dissolved only the bio-available fraction of Fe(III).